On an island in Argentina, wild boars love to grub for underground fungi. By distributing the fungal spores in their feces, scientists say, these non-native animals are helping invasive pine trees thrive.

The study, titled “Exotic mammals disperse exotic fungi that promote invasion by exotic trees,” took place on Isla Victoria in Argentina’s Nahuel Huapi National Park. In the early 1900s, people introduced about 135 exotic tree species to the island. Non-native wild boars followed in 1999 and now run rampant in tree plantations.

Pines need ectomycorrhizal (EM) fungi to flourish. So the authors wondered if the boars’ appetite for fungi contributed to the tree invasion. The team collected boar feces near tree plantations, then planted pine seeds in pots and added ground-up feces. After the seedlings grew, the researchers analyzed the root tips.

Many of the boars’ fecal samples contained EM fungal spores, and the team found the fungi growing on about one-third of the seedlings “fertilized” with boar feces. “This can be categorized as a case of invasional meltdown,” the authors write in PLOS ONE, “where the presence of one exotic species (in this case invasive mammals) exacerbates the impact of other exotic species”. — Roberta Kwok | 3 July 2013